A DC power supply device includes: a rectifier circuit; a reactor connected at one end to one output terminal of the rectifier circuit; a charging unit including a first and second switching element connected in series between another end of the reactor and another output terminal of the rectifier circuit, the charging unit configured to charge a first and second capacitor connected in series between output terminals to which a load is connected; and a control unit that controls the charging unit. The control unit sets, based on the timing at which the zero-crossing occurs, a dead time in which both the and second switching element are off, and when states of the first and second switching element at a time of occurrence of the zero-crossing match a predetermined set of states, reverses the states of the first switching element and the second switching element.

This refrigeration device comprises: a high temperature side refrigerant circuit in which a high temperature side refrigerant circulates; a low temperature side refrigerant circuit in which a low temperature side refrigerant circulates; and a cascade heat exchanger that cools the low temperature side refrigerant with the high temperature side refrigerant. In the low temperature side refrigerant circuit, a low temperature side decompressor is disposed downstream of the cascade heat exchanger and a temperature sensor is installed in a piping portion between the cascade heat exchanger and the low temperature side decompressor.

A system and a method for controlling temperature inside electrical and electronics systems. The method includes sensing temperature of an inverter section by a temperature sensor, the inverter section including one or more electronic components. The method also includes determining, by a microcontroller, a temperature zone based on the sensed temperature and transmit a command to an inverter based on the temperature zone. The method further includes controlling speed of a compressor by an inverter based on the command.

A heating, ventilation, and/or air conditioning (HVAC) system includes a mobile air conditioning unit configured to separately dock with each docking station of a plurality of docking stations. The mobile air conditioning unit includes a refrigerant circuit configured to condition an airflow to produce a conditioned airflow and a transportation system configured to autonomously relocate the mobile air conditioning unit.

A refrigerating and air-conditioning apparatus that performs defrosting operation, the refrigerating and air-conditioning apparatus including: a refrigerant circuit in which a compressor, a first heat exchanger, an expansion device, a second heat exchanger, and a four-way valve are connected to each other by pipes to allow refrigerant to circulate through the refrigerant circuit; a temperature sensor configured to measure a temperature of the compressor; and a heat generation control unit configured to increase a temperature of the compressor when the heat generation control unit detects a decrease in a value measured by the temperature sensor in defrosting operation performed on the first heat exchanger.

An energy efficient heat pump for a heating, ventilation, and air conditioning (HVAC) system includes a vapor compression circuit, a heat exchanger of the vapor compression circuit configured to place a working fluid in a heat exchange relationship with an air flow directed across the heat exchanger, and a conduit system of the vapor compression circuit. The conduit system of the vapor compression circuit is configured to direct the working fluid into the heat exchanger and to receive the working fluid from the heat exchanger, wherein the conduit system is configured to direct the working fluid into the heat exchanger to place the working fluid in a counterflow arrangement with the air flow directed across the heat exchanger in a cooling mode of the heat pump and in a heating mode of the heat pump.

A heat pump device includes a compressor that compresses refrigerant, a motor that drives the compressor, an inverter that applies a desired voltage to the motor, and an inverter controlling unit that generates a pulse width modulation signal for driving the inverter, has, as operation modes, a heating operation mode performing heating operation of the compressor and a normal operation mode performing normal operation of the compressor to compress the refrigerant, and periodically changes carrier frequency, that is frequency of a carrier signal, in the heating operation mode.

A power conversion device includes a rectification unit that rectifies first alternating current (AC) power supplied from a commercial power supply, a capacitor connected to an output end of the rectification unit, an inverter that converts power output from the rectification unit and from the capacitor into second AC power, and outputs the second AC power to a load including a motor, which inverter is connected to both ends of the capacitor, and a control unit that controls operation of the inverter to output the second AC power from the inverter to the load to reduce current flowing to the capacitor, which second AC power includes a pulsation that depends on a pulsation of power flowing from the rectification unit to the capacitor. No discharge circuit and no overvoltage protection circuit are provided for the capacitor.

A motor-driven compressor and a housing for the motor-driven compressor are provided. A power line connector and a communication line connector are arranged on an external surface of a housing. A first terminal of an interlocking communication line is located in the power line connector. A second terminal of the interlocking communication line is located in the communication line connector. The interlocking communication line is routed on the external surface from the first terminal to the second terminal.

A method initializes a defrosting operation in a refrigeration appliance having a speed-controlled compressor. The method includes the steps of: a) starting up the compressor at a speed set to an initial value, b) adjusting the speed of the compressor in order to prevent a temperature in a storage chamber of the refrigeration appliance from deviating from a target temperature, c) monitoring a deviation between an adjusted speed and the initial value, and d) deciding that defrosting is necessary if the deviation exceeds a limit value.